Grained, patterned or finely structured plastic skins are known as surfaces for objects and are, for example, used for interior trims in vehicles, here often as relatively soft underfoamed foils with pleasant haptics, for instance, for the covering of dashboards or the inner shells of doors, et cetera. When correspondingly adapted in strength and design, such foils are quite naturally also used for other high-quality coated goods.
In the state of the art, different processes are known for the production of such plastic skins, for example, rolling or embossing methods for the production of “endless” foil tracks made of thermoplastic plastic or methods for the production of machine-produced individual molded skins, that is, of plastic molded components.
In the rolling and embossing methods, a thermoplastic foil provided as a sheeting is provided with a three-dimensionally structured, embossed surface, that is, approximately a grained “leather” surface, with the aid of an embossing roller.
Machine-produced molded skins here denote more or less rigid molded plastic components which, for example, are produced by a variety of sintering or spraying methods in mold tools in which one or more liquid or powder components are deposited in a form and react/harden there. Machine-produced molded skins are thus also created by rotation sintering, for example, by methods for producing so-called slush-skins.
In these machine-produced methods it is also possible to determine the surface structure/texture, that is the surface of the plastic skin, that is, the approximate appearance of a grain, and the geometry of the entire component in a single forming process during manufacture. For this, the grain structure and component geometry are introduced into a molding form as a negative, the plastic skin is formed by a sintering or spraying process and removed thereafter.
The sheeting as well as the molded skins are generally provided with a layer of plastic foam on their back side, either after embossing or after insertion/deep-drawing into the component mold (sheeting) or already in the molding in which the plastic skin is manufactured (molded skins). Of course, other processes such as carding processes are known for foam-coating. Because of the subsequent back-foaming, an already reasonably rigid three dimensionally formed component results. The back-foaming here only represents one possibility of forming a support structure for the plastic skin. Likewise, adhesive bonding of structure-support elements of hard plastic is known.
U.S. Pat. No. 7,192,543 discloses a method for manufacturing machine-formed melt bodies/cast bodies, such as dashboards, door panels, or glove compartments, in which a divided bottom mold is initially and at least partially provided with an elastic foil, which covers the seams in the form, and which has a texture on its inner side, for example, a leather texture. A reactive mixture, which then forms the outer skin of the component, is sprayed onto the elastic foil before further reinforcements or foam layers are applied by means of different spraying or melting methods.
Usually, the molded skins with the support structure are cleanly worked on after the manufacturing process, that is any possible skin edges are cut off, and in dashboards, for example, the necessary cavities and holes for instruments, switches, trim strips, radios, et cetera are produced. Thereafter, for example, all switches and signal elements are individually installed into the dashboard and wired, that is, they are provided with connecting lines which are then connected during installation into the vehicle. The same is true for the installation of instruments, illuminants, speakers, et cetera. Trim strips and holders must also still be affixed.
Overall, substantial effort, a number of time and cost intensive manufacturing steps, and a logistical plan are still required prior to the transfer of an installation-ready dashboard, door insets, or similar components with functional elements to the subsequent processing operation, here the vehicle manufacturer.
To reduce the manufacturing effort, it has already been suggested to connect electrical conductors or thin membrane circuits, that is, foils provided with thin, deposited or adhesively bonded metallic conductors, directly to the back side of the molded skins or foils before or after the back-foaming, that is essentially to cover or laminate.
Thereby, the problem results that during the joining of the two different materials (molded skins or foils and conductors), the decor surface, that is the surface of the plastic skin which can be seen from outside, is damaged by the contact pressure during the laminating/covering process.
Further, there exists the problem that the materials leave markings on the decor surface when they are laminated with temperatures that are too high, and when individual materials having different shrinkage are laminated/covered and cool down at different rates.
Further, the problem persists that when stored in a warm environment, the molded skins or foils have different thermal expansion coefficients and, as a result thereof, a second track, which is possibly laminated behind the decor surface, becomes visible.
Further, there exists the problem that the decor surface experiences buckling after manufacturing and laminating with a conductor because of the different rigidity of the materials.
Furthermore, there is the problem that certain regions of the surface, especially in surfaces which are produced by the slush-process (rotation sintering), become creased during demolding because of the different degrees of rigidity.
Further, there exists the problem that the hard to access regions of a molded skin cannot be laminated/covered with a membrane circuit or a conductor, since accessibility of the back side is not given.